The GP2Y0A21 Sharp distance sensor is a great way to add obstacle avoidance or motion sensing to your robot or any other project. With a detection range of 4″ to 32″ (10 cm to 80 cm) and an analog voltage indicating the distance, this sensor is very easy to use.
The Sharp distance sensors are a popular choice for many projects that require accurate distance measurements. This IR sensor is more economical than sonar rangefinders, yet it provides much better performance than other IR alternatives. Interfacing to most microcontrollers is straightforward: the single analog output can be connected to an analog-to-digital converter for taking distance measurements, or the output can be connected to a comparator for threshold detection. The detection range of this version is approximately 10 cm to 80 cm (4″ to 32″).
The GP2Y0A21 uses a 3-pin JST PH connector. It is also possible to solder three wires to the sensor where the connector pins are mounted. When looking at the back, the three connections from left to right are power, ground, and the output signal.
- Operating voltage: 4.5 V to 5.5 V
- Average current consumption: 30 mA (note: this sensor draws current in large, short bursts, and the manufacturer recommends putting a 10 µF capacitor or larger across power and ground close to the sensor to stabilize the power supply line)
- Distance measuring range: 10 cm to 80 cm (4″ to 32″)
- Output type: analog voltage
- Output voltage differential over distance range: 1.9 V (typical)
- Update period: 38 ± 10 ms
- Size: 44.5 mm × 18.9 mm × 13.5 mm (1.75″ × 0.75″ × 0.53″)
- Weight: 3.5 g (0.12 oz)
Linearizing the output
The relationship between the sensor’s output voltage and the inverse of the measured distance is approximately linear over the sensor’s usable range. The GP2Y0A21YK datasheet (374k pdf) contains a plot of analog output voltage as a function of the inverse of distance to a reflective object. You can use this plot to convert the sensor output voltage to an approximate distance by constructing a best-fit line that relates the inverse of the output voltage (V) to distance (cm). In its simplest form, the linearizing equation can be that the distance to the reflective object is approximately equal to a constant scale factor (~27 V*cm) divided by the sensor’s output voltage. Adding a constant distance offset and modifying the scale factor can improve the fit of this line.
- Maximum range: 80 cm
- Minimum range: 10 cm
- Sampling rate: 26 Hz1
- Minimum operating voltage: 4.5 V
- Maximum operating voltage: 5.5 V
- Supply current: 30 mA2
- Output type: analog voltage
- Output voltage differential: 1.9 V
1Typical; can be as low as 21 Hz.
2Average; this sensor draws current in large, short bursts, which is why it is recommended a 10 µF capacitor or larger be placed across power and ground close to the sensor.
Note: The GP2Y0A21YK0F model is a lead-free, RoHS-compliant version of the Sharp GP2Y0A21 Distance Sensor. The manufacturer recommends you insert a bypass capacitor of 10 µF or more between Vcc and GND near this sensor to stabilize your power supply line.